tools/vm/page_owner_sort.c: support sorting by stack trace

This adds the ability to sort by stacktraces.  This is helpful when
comparing multiple dumps of page_owner taken at different times, since
blocks will not be reordered if they were allocated/free'd.

Link: https://lkml.kernel.org/r/20211124193709.1805776-2-seanga2@gmail.comSigned-off-by: Sean Anderson <seanga2@gmail.com>
Cc: Zhenliang Wei <weizhenliang@huawei.com>
Cc: Changhee Han <ch0.han@lge.com>
Cc: Tang Bin <tangbin@cmss.chinamobile.com>
Cc: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yinan Zhang <zhangyinan2019@email.szu.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/vm/page_owner_sort.c

@@ -29,7 +29,6 @@ struct block_list {
 	int page_num;
 };
 
-static int sort_by_memory;
 static regex_t order_pattern;
 static struct block_list *list;
 static int list_size;
@@ -134,13 +133,16 @@ static void add_list(char *buf, int len)
 
 static void usage(void)
 {
-	printf("Usage: ./page_owner_sort [-m] <input> <output>\n"
-		"-m	Sort by total memory. If this option is unset, sort by times\n"
+	printf("Usage: ./page_owner_sort [OPTIONS] <input> <output>\n"
+		"-m	Sort by total memory.\n"
+		"-s	Sort by the stack trace.\n"
+		"-t	Sort by times (default).\n"
 	);
 }
 
 int main(int argc, char **argv)
 {
+	int (*cmp)(const void *, const void *) = compare_num;
 	FILE *fin, *fout;
 	char *buf;
 	int ret, i, count;
@@ -149,10 +151,16 @@ int main(int argc, char **argv)
 	int err;
 	int opt;
 
-	while ((opt = getopt(argc, argv, "m")) != -1)
+	while ((opt = getopt(argc, argv, "mst")) != -1)
 		switch (opt) {
 		case 'm':
-			sort_by_memory = 1;
+			cmp = compare_page_num;
+			break;
+		case 's':
+			cmp = compare_stacktrace;
+			break;
+		case 't':
+			cmp = compare_num;
 			break;
 		default:
 			usage();
@@ -221,10 +229,7 @@ int main(int argc, char **argv)
 		}
 	}
 
-	if (sort_by_memory)
-		qsort(list2, count, sizeof(list[0]), compare_page_num);
-	else
-		qsort(list2, count, sizeof(list[0]), compare_num);
+	qsort(list2, count, sizeof(list[0]), cmp);
 
 	for (i = 0; i < count; i++)
 		fprintf(fout, "%d times, %d pages:\n%s\n",